Thread: The Conical Pendulum

I'm stuck on this question:

A light inextensible string AB of length 3l has its ends fixed to two points A and B which are in a vertical line with A a distance l above B. A smooth ring of mass m is threaded on the string and is made to move in a horizontal circle centre B with a constant speed. Calculate the tension in he string and the speed of the ring.

When I tried to calculate th tension I found that I needed either the radius of the circle of the diatance from either A or B to the ring, which I don't have. Have I missed something in the question? Could someone help please?

Originally Posted by free_to_fly

I'm stuck on this question:

A light inextensible string AB of length 3l has its ends fixed to two points A and B which are in a vertical line with A a distance l above B. A smooth ring of mass m is threaded on the string and is made to move in a horizontal circle centre B with a constant speed. Calculate the tension in he string and the speed of the ring.

...

I've attached a sketch of the situation as I understand it.

If I'm right the string forms a right triangle where the sides x and y have the length 3l:

....... [1]

....... [2]

From [1] you get: . Substitute this term into [2]:



That means which is the radius of the circle.